Early mobile communication devices employed analog radio transmission such as Advanced Mobile Phone System (AMPS), for example. Such analog technologies were sufficient for an emerging mobile communications consumer market. However, within a relatively short period of time, millions of new mobile communications subscribers, demanding more and more airtime, pushed the existing analog technology to a capacity limit or ceiling. As a consequence, dropped calls and busy signals became common, which fueled a demand for an improved mobile communication network.
In response to the demand, industry developed digital wireless technologies that could accommodate the increased network traffic within a limited amount of radio spectrum. For example, technologies such as Global System for Mobile (GSM) employing Time Division Multiple Access (TDMA) were developed, wherein a time-sharing protocol was employed to provide three to four times more capacity than the existing analog technologies. In general, TDMA employs a technique wherein a communication channel is divided into sequential time slices. Each user of a channel is provided with a time slice for transmitting and receiving information in a round-robin manner. For example, at any given time “t,” a user is provided access to the channel for a short burst. Then, access switches to another user who is provided with a short burst of time for transmitting and receiving information. The cycle of “taking turns” continues, and eventually each user is provided with multiple transmission and reception bursts.
Shortly after TDMA was introduced, Code Division Multiple Access (CDMA) was developed, and represented an enhanced solution to the analog transmission deficiencies. Code Division Multiple Access provides for “true” sharing, wherein one or more users can transmit and receive concurrently. Code Division Multiple Access provides sharing via employing spread spectrum digital modulation, wherein a user's stream of bits is encoded and spread across a very wide channel in a pseudo-random fashion. The receiver is designed to recognize and undo the randomization in order to collect the bits for a particular user in a coherent manner. Code Division Multiple Access provides approximately ten times the capacity of the analog technologies, and enables increased voice quality, broader coverage and increased security. Today, CDMA is the prevalent technology employed in mobile systems.
Technological advances in the electronics and computer industries, including smaller components, reduced power consumption, and the Internet, for example, have driven the mobile communications industry to further GSM and CDMA technologies, and to explore other technologies. One such improvement includes EDGE (Enhanced Data-Rates for GSM Revolution) technology. The evolution of GSM to EDGE mitigates various issues associated with voice traffic bandwidth and provides higher data throughput, affording for more efficiency and higher performance. For example, EDGE provides for data rates up to 384 Kbps (with a bit-rate up to 69.2 Kbps per timeslot) over broadband. In addition, EDGE provides for more robust services such a Short Message Service (SMS) and Multimedia Message Service (MMS) for messaging, XHTML (including WAP) browsing, Java applications, FM radio reception, video streaming, and voice and image recording technologies.
Another result of continued efforts to improve the mobile communications includes the International Telecommunications Union's adoption of an industry standard for third-generation (3G) wireless systems that can provide high-speed data rates (e.g., for data transmission and Internet use) and new features. Currently, three operating modes (CDMA2000, WCDMA and TD-SCDMA) based on CDMA technology are being developed. CDMA2000 technology provides a relatively simple, quick, and cost effective path to 3G service. CDMA2000 1× technology supports voice and data services over a standard CDMA channel. Additionally, it provides up to twice the capacity (e.g., peak data rates up to 153 kbps and projected peak data rates up to 307 kbps, without compromising voice capacity) of the earlier CDMA networks. The additional capacity accommodates the continuing growth in the wireless Internet market. Moreover, CDMA2000 1× provides longer standby times and is backwards compatible. CDMA2000 1× EV-DO technology provides a data optimized version of CDMA2000 with peak data rates over 2 Mbps and an average throughput of over 700 kbps, which is comparable to DSL and can support video streaming and large file downloads. WCDMA and TD-SCDMA represent more complex enhancements that can entail more costly and complex components, new network designs, and longer verification and validation periods.
Current technologies within the global mobile communication community include cellular, Personal Communication Service (PCS) and Global Personal Systems (GPS), for example. Cellular communication is typically associated with frequencies around 850 MHz. Personal Communication Service is typically associated with frequencies around 1900 MHz. Global Personal System is typically associated with frequencies around 1600 MHz.
Recent obstacles in the mobile communications domain include producing mobile communications products comprising a combination of technologies. For example, a consumer can concurrently subscribe to more than one service such a cellular and PCS services. Rather than having to obtain multiple devices, wherein each device accommodates an individual service, the consumer may desire one device that is capable of satisfying multiple services. In another example, an individual product that is adequate for a particular subscribed service (e.g., cellular) can become inadequate if the consumer decides to cancel the service and subscribe to a different service (e.g., PCS). The foregoing examples depict two services, however a consumer may desire a mobile communication device that provides cellular, PCS, GPS and/or Bluetooth technologies for communication over GSM, GPRS (General Packet Radio Service) and/or EDGE networks.
Combining technologies into a mobile communication device can additionally increase product size, via implementing various antennas, switching circuitry and processing technology, in a market that demands size reduction. In addition, providing multiple antennas can introduce interference via antenna coupling and re-radiating signals, which can degrade system performance and increase static in a market that demands clearer communication and less drop offs.